Every filing season, taxpayers hand the government more than they owe simply because they never claim deductions they qualify for. A deduction lowers the income the IRS taxes you on, so a $1,000 deduction saves you your marginal tax rate times $1,000 — roughly $220 if you sit in the 22% bracket. The four below are among the most commonly overlooked, and for each one we cover what the rule actually is, who it applies to, and a worked example so you can see the dollars.
One distinction up front, because it decides whether several of these even matter for you: some deductions are "above the line" (technically adjustments to income) and you can claim them whether or not you itemize, while others are itemized deductions that only help if your total itemized deductions beat the standard deduction. We flag which is which as we go.
1. Home Office Deduction
If you are self-employed and use part of your home regularly and exclusively as your principal place of business, you can deduct the cost of that space. The word that trips people up is "exclusively": a spare bedroom that doubles as a guest room or a kitchen table you also eat at does not qualify. The space has to be used for business and nothing else.
The IRS offers two ways to calculate it. The simplified method lets you deduct a flat $5 per square foot, for up to 300 square feet, for a maximum deduction of $1,500. The regular method instead deducts the actual percentage of your home used for business applied to real costs (a share of rent or mortgage interest, utilities, insurance, and depreciation), which can be larger but requires far more recordkeeping on Form 8829.
Worked example. Say you carve out a 150-square-foot office used only for your freelance work. Under the simplified method your deduction is 150 × $5 = $750. If your actual home costs run high — high rent in a city, for instance — running the regular method might beat that, so it is worth calculating both. One important caveat: this deduction is generally for the self-employed. Since the 2018 tax law, most employees who work from home for an employer can no longer deduct a home office on their federal return.
2. Student Loan Interest
If you paid interest on a qualified student loan, you can deduct the lesser of $2,500 or the amount of interest you actually paid during the year. The best part: this is an adjustment to income, so — per the same IRS guidance — you can take it even if you do not itemize. Your loan servicer typically reports the interest you paid on Form 1098-E.
The deduction phases out at higher incomes. For 2025, it is gradually reduced once your modified adjusted gross income (MAGI) climbs between $85,000 and $100,000 for single, head of household, or qualifying surviving spouse filers, and between $170,000 and $200,000 if you file a joint return — above the top of those ranges, the deduction disappears entirely. (Note that you cannot claim it at all if you file married filing separately, or if someone else can claim you as a dependent.)
Worked example. A single filer with a MAGI of $60,000 who paid $1,400 in student loan interest deducts the full $1,400 — they are below the phaseout, and they keep this even while taking the standard deduction. Someone who paid $3,000 in interest can still only deduct the $2,500 cap. A single filer at a MAGI of $92,500 — halfway through the $85,000–$100,000 phaseout — would see roughly half of their otherwise-allowable deduction.
3. Medical and Dental Expenses
Out-of-pocket medical costs are deductible, but only the portion that is large relative to your income. You can deduct, on Schedule A (Form 1040), the amount of your unreimbursed medical and dental expenses that exceeds 7.5% of your adjusted gross income (AGI). Because this is an itemized deduction, it only helps if your total itemized deductions exceed your standard deduction — so it most often comes into play in a year with major unreimbursed costs.
Qualifying expenses are broader than many people assume: they include payments to doctors, dentists, surgeons, and other practitioners; prescription medications; hospital and long-term care; many medical aids such as glasses, hearing aids, and wheelchairs; and even mileage driven for medical care (the IRS sets a medical mileage rate of 21 cents per mile for 2025). Health insurance premiums you paid with after-tax dollars can also count. What does not count: anything reimbursed by insurance, and generally cosmetic procedures.
Worked example. With an AGI of $50,000, your 7.5% floor is $3,750. If you racked up $10,000 in qualifying unreimbursed medical bills, you can deduct $10,000 − $3,750 = $6,250. If instead you only had $3,000 of expenses, you get nothing here, because you never cleared the floor.
4. Charitable Contributions
Gifts to qualified organizations are deductible if you itemize your deductions — and not just cash. The fair market value of donated goods (clothing, household items, furniture in good used condition) counts, as do out-of-pocket costs you incur while volunteering. That includes mileage: when you drive your own car in service of a qualified charity, the IRS lets you deduct 14 cents per mile. (Your time and the value of your services, by contrast, are never deductible.)
There are ceilings. Per the IRS, cash contributions to public charities are generally deductible up to 60 percent of your adjusted gross income under current law, while lower limits — commonly 30 percent of AGI (and in some cases 20 percent or 50 percent) — apply to certain noncash contributions and gifts to organizations such as private foundations. Documentation matters too: keep receipts, and for any single contribution of $250 or more you need a written acknowledgment from the organization.
Worked example. Suppose over the year you donate $1,200 in cash to your church, drop off clothing with a fair market value of $300 at a thrift store run by a qualified charity, and drive 200 miles delivering meals for a food bank. Your deductible total is $1,200 + $300 + (200 × $0.14 = $28) = $1,528 — assuming your overall itemized deductions exceed the standard deduction. Get the written acknowledgment for that $1,200 cash gift, since it is over the $250 threshold.
The bigger question: itemize or take the standard deduction?
Three of the four deductions above (home office is the exception — it lives on your business schedule) only deliver a benefit if you itemize. Itemizing means adding up your deductible costs — state and local taxes, mortgage interest, medical expenses over the 7.5% floor, and charitable gifts — and claiming that total instead of the flat standard deduction. You take whichever is larger. For many filers the standard deduction wins, which is exactly why these itemized write-offs go unclaimed. But in a year with a big medical bill, generous giving, or high mortgage interest, the math can flip, and the only way to know is to run both.
A practical move: keep a simple folder (digital or paper) through the year for receipts, your Form 1098-E for student loan interest, mileage logs for medical and charitable driving, and acknowledgment letters from charities. When filing season arrives you will have what you need to claim every dollar you are entitled to — and the documentation to back it up if the IRS ever asks.
This article is general educational information, not tax, legal, or financial advice. Tax rules, dollar limits, brackets, and phaseout thresholds change from year to year and depend on your individual situation. Figures cited here reflect the 2025 tax year as published by the IRS at the time of writing. Verify current amounts on IRS.gov and consult a qualified tax professional before making decisions about your own return.